GRASS GIS (Geographic Resources Analysis Support System) is a free, open source geographical information system (GIS) capable of handling raster, topological vector, image processing, and graphic data.

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6
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66 views

Is it possible to generate a boustrophedon pattern which fill a vector Region with GRASS?

Every thing is in the title... I have a vector region in GRASS. And I would like to generate a vector (a polyline) beeing the bostrophedon pattern which fill this region. In the picture bellow, I ...
4
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44 views

What Does the Cell Value in a Composite Raster Mean?

When I make a composite raster in QGIS using the GRASS r.composite tool and then click on a certain cell I get these values in the blue/green/red/composite rasters: blue = 124 green = 124 red = 172 ...
4
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247 views

How to create a topologically correct dataset in PostGIS (with GRASS)?

I have shapefiles which I have loaded in postgis and now i am trying to use geometric function in postgis like ST_intersect and they fail because the data is not topological correct. I have tried to ...
3
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70 views

Extract representative slope profiles from hillslope polygons

With the help of the Whitebox Geospatial Analysis Tools I was able to easily extract hillslopes from a river network in combination with a flow direction map. Now I would like to extract ...
3
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0answers
22 views

execute binary from grass shell?

I am new to grass and could really use some help with my problem. I am using hydrologic modeling software, and it include a grass program that I need to run from the grass shell. My question is, how ...
3
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31 views

Error message retrieval in grass.read_command

I am writing a script in python and would like to get the error messages of the function grass.read_command for seeing why it is not working. I found a webpage ...
3
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52 views

Option for 360 degree movie embedded in Open Source GIS software?

Is there any Open Source GIS software available to embed 360 degree movies with the map? For a COTS example, there is the Active Link Vision (ALV) extension for ArcGIS from IWANE.
3
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86 views

IS it possible to run GRASS commands in the QGIS graphical modeler?

I have a geoalgorithm set up in the graphical modeler and everything runs except for the GRASS commands. It is really frustrating because when I execute these commands on their own they work just fine ...
2
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44 views

QGIS-GRASS firespread simulation module

I'm trying to do some fire spread simulations in QGIS with GRASS fire spreading simulation module. QGIS ('Processing Toolbox' > 'Geoalgorithms' > 'Misc' > 'Fire spreading simulation') GUI. Already ...
2
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36 views

3D interpolating

Our final year project domain is soil contamination modeling. We collected soil samples at the depths of 0.3 cm ,0.5cm , 1cm , 1.5 cm in about 25 locations. We considered 8 contaminants- p h, sodium, ...
2
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93 views

Import vtk file in grass gis

last summer I made the relief of a cave, and at this time I returned with Therion software. This survey is in 3d and I can save it in the formats .Lox, .3d, vtk. I would like to import it in grass or ...
2
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38 views

GRASS 6.4.4 vector command in crashes QGIS 2.4 (g.gisenv.exe has stopped working)

I am running Windows 8.1 64 bit, and have QGIS 2.4 and 2.6 installed. When I try to use a GRASS 6.4.4 vector command (specifically v.clean), I receive an error message in an endless loop, and the only ...
2
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30 views

infer the altitude from a DTM & finally provide it to point / evincere la altitudine da un DTM & finalmente fornirla a dei punti

I would like to complete a point vector's table with Z data. I am not able to take Z coordinate from a dtm (downloaded from ...
2
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0answers
187 views

QGIS 2.4 NVIZ Solution

I am going to ask this question better: What happened with NVIZ? I do not know the exact version that nviz stopped working but it seems around version 2 of QGIS. There are two ways to get to nviz in ...
2
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0answers
205 views

How to merge overlapping and duplicate lines from vector layer to one single line?

I used the "polygone to line" tool from QGis, to get a line-layer from this polygon-layer: unfortunatly this causes overlapping and duplicate lines, after I broke the qgis-export via GRASS into ...
2
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0answers
97 views

best method for gridding or interpolating elevation data

I wonder if someone can recommend the best method for gridding elevation data in QGIS, GRASS or similar. The elevation data I have is collected along 1m spaced lines at approximately 1 reading per ...
2
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140 views

3D visualization of terrain data and orthophoto using GRASS NVIZ via QGIS

How can I make 3D visualization of terrain data and orthophoto using GRASS NVIZ via QGIS? I am quite new with GRASS. I have only managed to get a 3D view of the terrain so far.
2
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0answers
54 views

QGIS doesn't recognize GRASS commands

When I try to use GRASS commands in QGIS, I get the following error message: Missing dependency.This algorithm cannot be run :-( This algorithm requires GRASS to be run. Unfortunately, it seems ...
2
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196 views

Problem loading output layer QGIS

Every time I run operations with temporary file output from the graphical modeler, I get the following error message: Oooops! The following output layers could not be open CLIP: ...
2
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0answers
68 views

Background (sky/terrain) of a viewshed

Is it possible to determine whether a point feature of a particular height would be backed by sky or by terrain? I've done the viewsheed analysis of a wind turbine. Now I would like to make a raster ...
2
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0answers
593 views

QGIS cannot open output layers

I have problem with QGIS 2.0.1. Everytime I run tool from SAGA or GRASS, I get exactly the same error, for example: Oooops! The following output layers could not be open Channel Network: ...
2
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66 views

QGIS V. parallel command using GRASS

I cannot offset a line to a specific decimal place, (ie only whole numbers can be inputted) Am I missing something here??
2
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0answers
77 views

Longest slope oriented to north?

I need a help with my homework. I have created digital elevation model from the shapefile. In QGis(Grass plugin) This is how far i can go. I have to find the longest slope oriented to North. I know ...
2
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217 views

how to make decent sense from scattered river depth measurements

I sampled river depth at scattered positions and I want to be able to make a map and GIS layers out of it. My problems are: As the river meanders the interpolation I do in scientific packages i,e. ...
2
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206 views

How can I create random concave polygons for test purposes?

In the context of generating random test data using QGIS (in a shapefile): I can generate random, continuous (adjacent) polygons by first creating n random points using ftools and then generating a ...
2
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448 views

How to specify cost attributes for network analysis in QGIS using the GRASS plugin?

I have a road dataset with information about the length, speed and drivetime for each segment. I use QGIS 1.9 with the GRASS plugin to do different types of network analysis, but how do I set up the ...
2
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1k views

How do I change from lat/long to a metric coordinate system in GRASS?

Yes, it's yet another transformation question. I am working with ASTER DEM data, which is LatLong WGS84. I want to process the DEM map into an STL file for use in a CFD simulation. The script I am ...
2
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120 views

How to create the fuel models & live fuel moisture rasters for Wildfire simulation?

Has anybody done wildfire modelling in GRASS? Where could I obtain / how do I create the fuel models and live fuel moisture rasters to determine rate of spread (r.ros)?
2
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28 views

How to remove coastlines from Admin 0 data set using GRASS?

I have a set of international borders that I would like to overlay on top of a different data layer that represents coastlines ("land" essentially). I would like to convert my Admin 0 polygons into ...
2
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603 views

GRASS GIS - r.water.outlet - What is my mistake?

I'm new to GIS - more so in GRASS GIS. I installed GRASS GIS 6.4.3svn in my Windows 7 machine. No problem in installation. Downloaded SRTM-Geotiff file Location, Mapset all o.k Used r.in.gdal to ...
2
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0answers
1k views

Simulate flood to assess Asset inundation footprints

I am trying to evaluate a number of flood gauges to assess at what levels of river height different flood risks would need to be issued. The gauges are currently set to warn of flood a couple of ...
2
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121 views

How to fix Graphserver warning “osmdb has no edges!”?

I'm really new to GIS. I have some shapefiles data that I'm trying to import in graphserver. I'm doing: gs_osmdb_compile output3.osm output3.osmdb And the result is: WARNING: osmdb has no edges!. ...
1
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32 views

QGIS, GRASS and WINDOWS 8

Good morning, I'm using QGIS 2.8.1 (Wien) on Windows 8 x64 bit. When I'm trying to lunch the GRASS plugin (6.4.3), Windows shows me the error g.mapset.exe has stop working, then after some times, ...
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0answers
25 views

Is it right to remove salt & pepper effect from a product produced by clean images?

I have two images from classification (different years) and I want to find the changes of land cover . I have cleaned the two images (salt and pepper). When I create a cross product of the category ...
1
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0answers
59 views

QGIS 2.8 problem accessing GRASS commands

QGIS 2.8.1 Win7 64 bit installed with osgeo4w-setup. I’m trying to run GRASS commands on a LIDAR raster layer but I get Missing dependency.... GRASS not installed in your system message each time. ...
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24 views

How to load “soil types” in QGis?

I want to show soil transmissivity per pixel. Thus, I determine water holding capacity of each pixel (ignored other effective parameters). Respectively, I wonder, What is the soil data format and How ...
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49 views

Hydropower Calculation

I have assigned the elevation and the volume flow to each point at a river (with v.to.db and v.what.rast). Now I want to calculate the Elevation difference between each pair of points and then ...
1
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0answers
20 views

What is the background processing of rainfall thresholding?

I want to create a flood map using Quantum GIS. First of all I create catchment area (flow accumulation). Then, I delineate a Channel Network by applying a threshold to flow accumulation. So I want to ...
1
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0answers
27 views

problem with running raster calculator in grassgis

When I was trying to do NDVI with grassGIS I faced a problem. I cannot run the raster calculation. When I looked to the command console I see that (Sat Feb 21 12:41:58 2015) r.mapcalc ddes = ( ...
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0answers
10 views

GRASS GIS: Network analysis doesn't work correctly

I got a problem with the Network Analysis function v.net.iso in GRASS. I tried it so many times but the function doesn't work correctly. I tried to calculate isolines via the function v.net.iso, based ...
1
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0answers
23 views

Raster Mosaicking GRASS Issue

I have a project where I have to download DEMs from USGS and mosaic them. So I downloaded them from EarthExplorer and imported them into GRASS. When I start the GUI version of r.patch using the ...
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0answers
13 views

r.water.outlet returning blank raster

I am trying to delineate a watershed using r.water.outlet. I have created a flow direction raster using r.watershed (threshold = 50) (cell size is 300m). I use this flow direction raster in ...
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32 views

Displaying a Digitial Elevation Model using GRASS GIS draped by an RGB Raster

I have the following: Digital Elevation Model from SRTM LANDSAT Imagery from the same area I wish to display the DEM draped with the raster band combination (3,2,1) using GRASS GIS. My ...
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0answers
65 views

Error when using r.watershed

When i am calculating LS Factor using Grass r.watershed the error "Raster map or group not found" (image below) keeps turning on. I don´t understand why this error happens if i am using a elevation ...
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0answers
50 views

QGIS and GRASS r.fill.dir processing times

I am new to the open source software and have performed analysis in ArcGIS in the past. I am learning as I go on this processes for OS. I am trying to calculate stream order (strahler) on a 1 gig ...
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75 views

How to extract percentage of land cover from a raster according to multiple shapefiles?

I have a raster map that represents land cover of a region, and different shapefiles (total 120) in the same region. I want to know the percentage of every land cover for each shapefile. For example, ...
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114 views

Assessing Flood Hazard Risk Zones using DEM

My Question: What is the best effective way to quickly estimate flood hazard risk areas using DEM data? Ideally I am looking for guidance to move forward and perform this process over large areas ...
1
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0answers
23 views

Distance between each feature from and every feature to in GRASS

In GRASS, v.distance calculate the minimum distance from each point feature in the 'from'-layer to the nearest feature in the 'to'-layer. I should instead calculate the minimum distance from each ...
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0answers
40 views

GRASS GIS G_malloc error

I am new to GIS. I downloaded GRASS and the sample data sets and am attempting to use the tutorial at: http://grasswiki.osgeo.org/wiki/Quick_wxGUI_tutorial. During the step, "Create a random ...
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0answers
34 views

GRASS GIS 7, Windows 8.1, Graphical Modeler, Export to Python

I need help. I´m trying to export my model made in Graphical Modeler in Grass GIS 7.0.0 beta3 to Python Script. The exported file contains only header.